Newbie question: is it possibile to split a library?

Yes, it is easy. Use "File➞Export ... as New Library", confirm that the Library works as you expect and contains what you want, and then delete from the first Library what was exported to make the second.

This page from the User Manualgoes into detail.

It may not be desirable or recommended, however. Larger Libraries are more useful than groups of smaller Libraries for most applications. Why are you splitting your Library? How do you use it?

That's a good reason 🙂 .

Yes. Select all of the Images you host which (presumably) are not yours, and run the "Export as Library" command. Pay attention to the options that appear. They are, iirc, self-explanatory, but feel free to ask if they are not.

NB: never change any file without having a complete and verified back-up.

But the other guy must have A3 or iphoto, otherwise he won't see anything.

Hi

Maybe I'm stupid, but as far as I can see, there is no option to Export to new library. I have iPhoto 11 version 9.4.3 on my laptop, and also the new IPhoto 11 version 9.5 and can't find an Export to new library option in either. The export option lets you export to a file, a slideshow or a web page.

Could you clarify, please?

Sorry, just spotted this is Aperture. I thought it was about iPhoto which is where I put the query. Is it possible to do it in IPhoto?

In iPhoto the only option is the paid version of

iPhoto Library Manager

That will let you create partial libraries. Or upgrade to Aperture. Aperture 3.5 will be able to open your iPhoto 9.5 library. But iPhoto Library Manager would be the less expensive option and is a very good addition to iPhoto - a great tool to have, if your library should need rebuilding or reconnecting referenced originals.